The present invention relates to a filter apparatus, and especially to a filter apparatus for filtering combustion air in internal combustion engines.
U.S. Patent Publication No. 2007/0131194 (=WO 2005/095783) describes a filter apparatus for filtering combustion air for an internal combustion engine. The filter element of this filter apparatus comprises a plurality of tubular filters that are covered by a housing cover. The filter walls of the tubular filters are formed of a porous filter material. On the outside of the tubular filters, the ambient air guided into the engine compartment flows in radially, such that dirt particles entrained in the air are deposited on the outside of the tubular filters. The filtered air in the tubular filters is discharged axially and fed into a plenum chamber, which communicates with the cylinder intake ports of the internal combustion engine. Since a plurality of tubular filters is provided, the filter surface is sufficiently large to keep the pressure drop between the unfiltered and the filtered side low.
Filter elements of this kind must be serviced at regular intervals because the filtration efficiency decreases as dirt accumulates along the filter wall on the unfiltered side or the pressure drop between the unfiltered and the filtered side continues to increase.